Companies like Weight Watchers have started creating low-calorie wine to appeal to the diet-conscious crowd. The trick with low-cal wine is that fewer calories usually just means a lower alcohol content, since alcohol makes up the majority of calories in wine [source: Tepper]. You'd think that sugar would be the major calorie-contributor in a drink like wine, but since alcohol contains more calories per gram than sugar -- almost twice as many! -- cutting the alcohol content is the most efficient way to cut the calories in a bottle of vino [source: Noelcke].

Weight Watchers wine, which launched in the U.K. and Australia in 2012, is around 8 percent alcohol, which is very low for wine [source: Tepper]. The company hasn't released calorie information for their wines, so it's hard to say exactly how many calories wine consumers are saving [source: Evon].

In the U.S., Skinnygirl, which you might know from its line of low-calorie cocktails, got in on the diet wine action also in 2012. It touts a 100 calorie glass, but it turns out that most 12 percent alcohol wines are already around 100 calories a glass, and 12 percent is a pretty common alcohol content for a bottle of wine, though some varieties can have higher alcohol levels and higher calories [source: Kaplan]. So, you can find a low-calorie wine without necessarily looking for a diet one.